Ahaha.....thanks. I have done the potato hack before. I tend to lose enormous amounts of weight if I do that, and most of my goals are muscle gain. I cannot take in more than about 1200 cal on a potato hack, so it is a 60% below maintenance cut in my case.

I tire quickly of all of the esoteric scientific battles on here....everyone that has ever peaked on their fitness will tell you that all of the theory and routines in the world are pointless without compliance and carry-through. Effort and discipline is everything. Science is only step one.

I cannot take in more than about 1200 cal on a potato hack, so it is a 60% below maintenance cut in my case.

As I said in the PD thread, I just started and realized that I need to eat at least 1.5kg or 2kg of taters to avoid severe caloric deficit. I usually eat one meal / day a la warrior diet minus the snacking, sometimes 2 meals. 2kg of boiled potatoes in one meal is not exactly going to happen ...

I tire quickly of all of the esoteric scientific battles on here....everyone that has ever peaked on their fitness will tell you that all of the theory and routines in the world are pointless without compliance and carry-through. Effort and discipline is everything. Science is only step one.

Well, yeah, I tend to agree here. Science is not even step one I suspect, it is an ever changing background discussion from which one can get inspired at some point but not fully rely on for the long haul.

Anecdotal:
I work in a grocery store, and was talking with a customer about the conditions that egg-laying hens are kept in. She was very concerned about it. Then she said, "I'm just doing the best I can. I was vegan for years, until my fingernails fell out, and I learned I can't do it anymore. So I'm trying to be as humane as I can."

I did the Vegan thing for 7 years and didn't suffer the problems that many people describe. However towards the end I craved the fat and grease of a plate of spicy chicken and it was all over for Vegan.

A great read is The Vegetarian Myth: Food, Justice, and Sustainability. It covers a lot of your issues.

anecdotal:
I work in a grocery store, and was talking with a customer about the conditions that egg-laying hens are kept in. She was very concerned about it. Then she said, "i'm just doing the best i can. I was vegan for years, until my fingernails fell out, and i learned i can't do it anymore. So i'm trying to be as humane as i can."

@Ripped: Actually, humans started building permanent housing before grains. First there was gardening and after that farming grains. The problem with grains then was that there needed first to be a method of collecting them in large quantities to make them worth anything. Then equipment for processing them, such as grinding stones, for storing them for longer periods without mice and rats and other rodents running away with it all. So the first permanent settlements were likely in areas with mild temperatures where fruit and vegetables could be harvested (almost) all year round.
All of which is kind of besides the point, I know.

As far as your points about gorillas: I'm very hesitant about drawing parallels between human and gorilla digestive tracts. Not because we're not relatives, but because even closely related animals can have wildly differently specialized diets. In general when observing an animal, it should be taken on it's own terms instead of jumping to conclusions about it's biology and behaviour based on another, similar species. I'm not a biologist or a zoologist, so I don't have first hand information on what the digestive track of a gorilla looks like or how it functions (from doing some googling, most popular links point to highly suspicious sites that talk about ape biology as a basis for eating vegetarian and not as a scientific study on how and why apes function). What I do know, however, is that it's commonly reasoned that the human brain grew because of the abundance of energy/nutritious food available for it and because of the need to use it. So it's not really that evolution weeded out the dumber ones, since the brain's an organ that can be and does develop throughout a person's life time. It's more like there was need for each individual in a group to use their nogging and continuously learn, move (since exercise improves your brain functions) and there was a LOT of food around to facilitate the brain's development. The current anthropological notion is that hunter-gatherers were (and are to some extent) the original affluent society. Just like the current affluence seems to breed taller and in some cases, heavier, people. Remember that this transformation of the brain took thousands of years. So it'll be really interesting to see how our current lifestyle and diet affects the shape our brains will have in another few thousand years.

As far as eating meat, not getting enough protein and so on and so forth go... welp, from what I've read (and heard on lectures), and this is largely based on what it currently known about how the human body works, so keep in mind that there is a positive bias with all scientific publication, it's hard not to get enough protein as an average, sedentary person if you eat greens, vegetables, fruit and nuts. In that order. Though if you're looking to experiment, looking into raw veganism might be your thing. There are a lot of vegetarian and vegan athletes, including Frank Medrano here, though I have to say I don't know how much they supplement with pea or soy protein (if at all).
Are there downsides to not eating meat? I would argue that it depends on your genetics and/or possibly your location. I have no idea how much plasticity there is in how your body adapts to your current environment and I don't know if there are studies made of that. What I mean is that generally people who live in those mild to humid areas of the world seem to thrive on just plants (there would need to be a comprehensive study on their B12 levels and not just the levels of B12 in western countries) however, people in northern parts of the world would seem to require at least some animal products in their diet. The recommendation is eggs and fish. When I was experimenting with raw veganism, it dried out the top layer of my skin completely (not to mention I felt kind of loopy, but that's a different story...) and apparently that's a common problem with us pale nordics. Adding eggs and meat back changed the situation immediately. I'd love to try out being vegan again if I was to move to a more tropical climate for a few years to see if my body would adapt to those surroundings. Eating fruit as a staple? Dr Lustig does make a very good case on how and why the sugar when eaten in fruit or berry form would be totally cool.

I'm very firmly of the opinion that the human brain evolved the way it did because propensities for language and conditional reasoning allowed us to be successful group hunters. And being successful hunters gave us the raw materials necessary to grow larger brains. Plants are fine with me, but eating brains and marrow gave us our start to becoming human, and hunting skills and tools got us as far as we've come. Now we're trying to go backwards, and with pretty good success.